1. Technical Field
This invention relates to a binocular visual simulator and, more particularly, to a binocular visual simulator for correcting eyeball aberration by using adaptive optics to form a chart image on both eyes.
2. Description of the Related Art
In order to solve the inconveniences of wearing glasses for eyesight correction, keratectomy, such as LASIK (laser in-situ keratomileusis), LASEK (laser assisted sub-epithelial keratomileusis), or PRK (photorefractive keratectomy) using excimer laser, prevails. However, even after keratectomy is performed, there frequently occurs that eyesight is not greatly improved, or light spreading (diffusion of focal point) is generated at night due to a side effect of the keratectomy though there is no problem in daytime eyesight.
When pupils are constricted in bright light condition as in the daytime, light passing through a portion near the center of the cornea is chiefly focused on the retina because light incident to a peripheral portion which is deviated from the center of the cornea is blocked by the pupil, thereby forming a clear image. When the pupil has dilated because the surroundings are dark as at night, light passing through the center of the cornea is focused on the retina, while light passing through the peripheral portion of the cornea is focused ahead of the retina. As a result, an image is not clear and looks opaque or light looks spread. The reason for these results from spherical aberration.
However, there is a problem in that a patient may have a burden of a surgical operation because the patient is unaware that how much will do light spreading occur at night before the patient is subject to a keratectomy operation.
For example, if eyesight is measured using an automatic eyesight measurement unit (e.g., a phoropter), some among a plurality of lenses are alternately inserted between the cornea and a chart, and eyesight is measured while watching a chart whose diopter has been corrected. Since the predetermined lenses correct only a diopter corresponding to low order aberration, a clear focus is formed on the retina when the pupil contracts as illustrated in (b) of FIG. 1, but a clear focus is not formed on the retina due to the aberration of a peripheral portion when the pupil dilates as illustrated in (a) of FIG. 1. Furthermore, there is no scheme for correcting high order aberration, that is, a scheme for focusing an image on the retina of a patient in the state in which high order aberration has been corrected, because only a diopter is corrected using the automatic eyesight measurement unit.
Furthermore, since a chart for eyesight measurement (or a chart) outputs an image including dark letters in a bright and white background, the pupil contracts when an image of the chart enters an eyeball, thereby making it difficult to measure eyesight in the state in which the pupil has dilated.
Furthermore, in eyesight measurement for a conventional eyesight correction operation, there is a problem in that it is difficult to precisely measure binocular eyesight simultaneously because eyesight measurement is performed on each of both eyes.